Vehicle heater with water pump venting

ABSTRACT

In a vehicle heating appliance, water is pumped as heat transfer medium through a heat exchanger that surrounds the combustion chamber. The water pump is mounted above the heat exchanger and pumps the water it axially receives into the heat exchanger through a tangential pump outlet pipe. To vent the pump, a connection hole with a small cross-section is provided in the top area of the pump part of the water pump. The connection hole leads to the system flow pipe. Any air bubbles accumulated in the pump chamber of the pump part reach the flow pipe through the connection hole, propelled by their own ascending force and helped by the geometric arrangement of the pump chamber and return pipe, including the connection hole, and/or additionally by the pressure difference between the pump chamber and the return pipe.

FIELD OF THE INVENTION

The present invention pertains to a vehicle heater with a combustionchamber, which is surrounded by a heat exchanger, through which water orwater with added antifreeze flows as the heat carrier. A water pumparranged outside on the heat exchanger pumps water, from a return pipeof a water circuit, through the heat exchanger. The water leaves theheat exchanger via a flow pipe after heating. Such vehicle heaters areusually used as auxiliary heaters in passenger cars, trucks, and buses,and also in recreational vehicles, small motorboats, constructionequipment, and airplanes.

BACKGROUND OF THE INVENTION

A fuel-air mixture is generated in the combustion chamber by means of afuel pump, a combustion air blower, and, e.g., a fuel evaporator. Duringthe combustion of the mixture, the thermal energy is released by a heatexchanger surrounding the combustion chamber to the heat carrier, whichis part of a heat carrier circuit.

Vehicle heaters should have a very compact design and meet a highstandard in terms of operating safety.

One special problem related to the usual vehicle heaters is the bleedingof the pump circulating the heat carrier, e.g., water, in the heatcarrier circuit, Air originating from the filling of the heat carriercircuit must be prevented from collecting or remaining within the pumpchamber of the pump part, not only to avoid undesired noises during theoperation, but especially to guarantee the desired throughput of thepump. The pump can be driven electrically by a pump motor.

In the usual vehicle heaters, the water pump has hitherto been arrangedunder the heat exchanger and consequently practically in the deepestarea of the entire water circuit. The consequence of this was that airbubbles that may be present in the area of the pump automatically roseup, so that they did not cause any interference at a higher point of thewater circuit. In view of the problem of the generation of air bubblesin the pump area, the water pumps were hitherto intentionally arrangedunder or next to the heat exchanger in order to guarantee the escape ofthe air bubbles due to this special installation position.

SUMMARY AND OBJECT OF THE INVENTION

The basic object of the present invention is to provide a vehicle heaterof the class described in the introduction, in which the water pump canbe arranged not only next to the heat exchanger, but also above it,without the risk of air bubbles collecting or remaining in the pump.

This object is accomplished according to the present invention in avehicle heater of the above-described class by the delivery side of thepump part of the water pump being connected in terms of flow via aconnection opening of small diameter to the flow pipe of the watercircuit.

The term "flow pipe" is related here to the entire heating system, sothat the "flow pipe" feeds the water just heated by the heat exchangerto the system having one or more heating heat exchangers (heatingelements). The "return pipe" is correspondingly the pipe which feeds thewater cooled, due to heating the surrounding environment by the heatingelement, to the heat exchanger for reheating.

Thus, the present invention creates a "bypass" between the delivery sideof the pump and the pipe via which the water just heated leaves the heatexchanger. The pressure occurring in this "flow pipe" is somewhat lowerthan in the pump chamber (the water has flown through the heatexchanger, e.g., along a spiral path), and over a section of the flowpipe between the pump chamber and the junction point of the smallconnection opening in the flow pipe).

Any air bubbles that may be present in the area of the pump are forcedby the pressure occurring there into the flow pipe because of theabove-mentioned differences in pressure, and they enter the system viathe flow pipe at a point that is remote from the water pump.

This removal of possible air bubbles operates especially reliably if theflow pipe is located higher than the pump part of the water pump, andthe connection opening is at the highest point of the pump chamber ofthe pump part in the installed position of the water pump. It isachieved due to this measure that air bubbles that may be present willcollect in the vicinity of the connection opening even in the state ofrest of the water pump, because water bubbles present in the pumpchamber will rise up and collect at the connection opening (unless theyhave already entered the flow pipe through the connection openingwithout the pump running), since the connection opening is located atthe highest point of the pump chamber.

If the connection opening between the pump chamber and the flow pipe isplaced at the highest point of the pump chamber, in which case the flowpipe is located even higher than the connection opening, it is possibleto install the water pump on top of the heat exchanger of the vehicleheater. If the water pump is not only to be placed on top of the heatexchanger, but it shall also be desired to arrange the pump next to theheat exchanger, this becomes possible according to the present inventionby providing--in the installed position of the water pump--a pocket atthe highest point of the pump chamber of the pump part, which point isalso the laterally outermost point of the pump chamber, and by providingthe connection opening at the highest and laterally outermost point ofthe pocket.

It can be imagined that in such a design, the air bubbles migrate to the"highest" point of the pump chamber, i.e., to the pocket, and finally tothe connection opening if the water pump is located on the top of theheat exchanger. If the water pump is arranged laterally next to the heatexchanger, in which case the water outlet connection piece of the pumpextends horizontally, any air bubbles that may be present will alsoreliably reach the connection opening, through which they can enter theflow pipe.

The connection opening preferably has a cross section of 0.5-3 mm². Aswas stated, the connection opening according to the present invention isa "bypass." The water flow passing through the connection openingrepresents a loss of circulation per se, because the water is not yetheated and yet enters the flow pipe of the system. However, the "leakageloss" is extremely small in the case of such a small cross-sectionalarea as indicated above, so that any reduction in the efficiency of thesystem is negligible.

It is obvious that the problems being discussed here are specific ofwater pumps which are used in vehicle heaters. The medium being pumpedis usually fed in in the axial direction in the water pumps beingdiscussed here, and it is pressed out by the pump impeller in the radialdirection, and the discharge from the pump chamber is arrangedtangentially.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a side view of a water pump with an inlet and an outlet andwith a pipe originating from the heat exchanger, wherein the water pumpis arranged on top of a partially represented heat exchanger of avehicle heater, and

FIG. 2 is a sectional view along line II--II in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows part of a prior-art heat exchanger 2 of a vehicle heater.The other parts of the vehicle heater are not shown here, because theyare not essential to the present invention. However, the person skilledin the art knows that a combustion air blower, a fuel pump, a controldevice, and the water pump 6 shown in FIG. 1 also belong to the vehicleheater, besides the heat exchanger 2 and the combustion chamber providedtherein.

The water pump 6 has an electric pump motor 8 with electric terminalsnot shown here, and a pump part 10, to which relatively cold water isfed axially via a system return pipe 4 in the direction of arrow P1. Thewater pump 6 is of a prior-art design and it does not need to bediscussed here in greater detail. A pump impeller (which was omitted inFIG. 2 for simplicity's sake) is located in a pump chamber 38 (FIG. 2)of the pump part 10. The pump impeller receives the water flowing inaxially to a low pressure side of the pump and delivers the water from ahigh pressure side radially to the outside, so that the water isdischarged via a tangentially arranged pump discharge connection piece12.

As is also apparent from FIG. 1 and FIG. 2, the water leaving the pumppart 10 via the pump discharge connection piece or end 12 (arrow P2 inFIG. 2) enters the heat exchanger 2 through a pipe connection or intakeend 14 and a hole 16.

As is shown in the bottom part of FIG. 2, the heat exchanger 2 has anouter jacket 20 and an inner jacket 22, between which an annular spaceor flow passage 24 is formed, and through which water W flows. Thecombustion chamber B is located inside the heat exchanger 2. The thermalenergy present in the combustion chamber B due to the flame reaches thewater W acting as a heat carrier via the inner jacket 22.

Guide ribs are usually formed within the annular space 24. These guideribs guide the water along the cylinder jacket-shaped annular space 24in a spiral pattern before the now heated water, leaves the heatexchanger 2 via a pipe connection or discharge end 18 to flow into asystem flow or heat exchanger discharge pipe 30 (arrows P3 and P4 inFIG. 1). The flow pipe 30 feeds the warm water to one or more heatingheat exchangers (heating elements).

To prevent air bubbles, which could considerably interfere with theoperation, from collecting in the area of the pump part 10, a bleedingmeans is provided according to the present invention, which makes itpossible to arrange the water pump 6 at any desired point, especially ontop of the heat exchanger 2 or to the side of the heat exchanger 2.

FIG. 1 shows the water pump in its installed position on top of the heatexchanger 2. As is apparent from FIG. 2, the flow pipe 30 has a portionwhich is located at a higher point than the pump chamber 38 of the pumppart 10 in the section plane of the pump part 10. A pocket 36 isprovided in a connection part between the flow pipe 30 and the pump part10 in the top right corner of the pump part 10.

A connection gap 34 is provided as a connection opening between the pumpchamber 38 and the flow pipe 30 at the top fight end of the pocket 36.The cross-sectional area of the connection gap 34 is 2 mm² in thisexemplary embodiment.

The pump impeller (not shown) in the pump part 10 rotates in thedirection of arrow P5 during operation in order to allow the water fedaxially into the pump part to flow into the annular space 24 of the heatexchanger 2 in the tangential direction via the pump dischargeconnection piece 12 in the direction of arrow P2.

If air bubbles are formed or are present in the area of the pump, theymigrate upward, especially with the pump not running, and theyautomatically reach the pocket 36. An air bubble L is shown as anexample in the area of the pocket 36 in FIG. 2. Since there is apressure gradient between the pump chamber 38 and the interior of theflow pipe 30, the air bubble L is pressed into the flow pipe 30, viawhich it will then be able to escape into the system in the upwarddirection. Only the uplift of the air bubble L acts when the pump is notrunning, as a consequence of which the air bubble L escapes into theflow pipe 30 because of the geometry shown in FIG. 2. During theoperation of the pump, the air bubble L is expelled from the pocket 36through the connection gap 34 because of the above-mentioned pressuregradient between the relatively high pressure Pr1 within the pocket 36and the relatively low pressure P2 within the flow pipe 30.

Because of the special design of the pocket 36 shown in FIG. 2 at thehighest point of the pump part 10 and also at the outermost point to theright of the pump part 10, the pump thus designed or the connectionbetween the pump part and the flow pipe can be arranged not onlyaccording to FIG. 1, i.e., above the heat exchanger 2, but also to theside of the heat exchanger. It is guaranteed even in this position nextto the heat exchanger that any air bubble can enter the flow pipe 30 andcan escape into the system. This becomes dear on rotating FIG. 2 by 90°counterclockwise. The water pump 6 is located in this case on theleft-hand side of the heat exchanger 2, and the connection gap 34 islocated, as before, at the point that is located higher than the otherareas of the pump chamber 38, but still below the flow pipe 30.

The arrangement shown in FIG. 2 can also be designed mirror-inverted,i.e., the pump discharge connection piece 12 may be located on theright-hand side in FIG. 2, while the pocket 36 and the connection gap 34are in the top left area of FIG. 2.

The pocket 36 described may be essentially as long as the pump chamber38 in the axial direction (i.e., at right angles to the plane of thedrawing in FIG. 2). However, the pocket 36 is preferably made very flat,i.e., 0.5 to 3 mm in length, in the axial direction. It will thuspreferably be located at the axial end of the pump chamber 38 which isfarther above in the case of sloped or vertical installation (angle ofthe axis of the heat exchanger relative to the horizontal direction) ofthe vehicle heater. In FIG. 1 this would be the right-hand axial end ofthe pump chamber in FIG. 1, i.e., the end that is farthest away from thepoint of fuel supply to the combustion chamber.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

I claim:
 1. A vehicle heater comprising:a heating circuit; a combustionchamber positioned in said heating circuit; a heat exchanger positionedin said heating circuit and around said combustion chamber, said heatexchanger including a flow passage, said flow passage having an intakeend and a discharge end; heat exchanger discharge pipe positioned insaid heating circuit and connected to said discharge end of said heatexchanger; pump means positioned in said heating circuit and for flowinga fluid through said heating circuit, said pump means including a highpressure side in communication with said intake end of said heatexchanger, said high pressure side of said pump means also includes aconnection gap providing fluid communication between said high pressureside and a portion of said heat exchanger discharge pipe.
 2. A vehicleheater in accordance with claim 1, wherein:said portion of said heatexchanger discharge pipe is positioned higher said pump means; said pumpmeans includes a pump chamber; said connection gap is positioned in ahighest point of said pump chamber when said pump means is in aninstalled position.
 3. A vehicle heater in accordance with claim 1,wherein:said pump means includes a pump chamber; said pump means definesa pocket positioned in a highest and outermost lateral point of saidpump chamber; said connection gap is positioned in a highest point ofsaid pocket.
 4. A vehicle heater in accordance with claim 1,wherein:said connection gap an a narrowest flow cross section of 0.5 to3 mm².
 5. A vehicle heater in accordance with claim 1, furthercomprising:a return pipe connected to a low pressure side of said pumpmeans, said return pipe delivering water from another heat exchanger;said pump means being positioned between said return pipe and saidintake end of said heat exchanger.
 6. A vehicle heater in accordancewith claim 1, wherein:a heat carrier flows though said heating circuit,said connection gap has a narrowest flow cross section of a size largeenough for passage of gas bubbles in said heat carrier, said narrowestflow cross section is also of a size small enough to restrict heatcarrier flow through said connection gap to a magnitude where anyinefficiencies caused by said heat carrier flow though said connectiongap is more than compensated by efficiencies gained by removing said gasbubbles.